Mawile, The Deceiver Pokémon. It uses its docile-looking face to lull foes into complacency, then bites with its huge, relentless jaws. It's huge jaws are actually steel horns that have been transformed. When the foe least expects it, it chomps it with its gaping jaws.

Putting EV's into speed allows Mawile to outrun
skarmory's and weezings (though it takes 164 speed
EV's to outrun a no speed Skarmory, some Skarmory's do
carry speed so you may need more than 164).
Taunt screws up a non-fire blast Weezing and pretty
much permanantly screws a Skarmory (due to its only
offensive move usually being Drill peck).
Since Mawile is a pure steel type, its common
weaknesses are fire and ground types, so common moves
like Earthquake will do a lot of damage, if not faint
it.
Mawile's stats doesn't make it the greatest pokemon in
game (380 sum of base stats), though it can make an
effective baton passer. If Mawile isn't knocked out
before it gets to baton pass, one swords dance/iron
defense should be enough to pass to a physical
sweeper/physical wall.
In the first slot, there are two moves that could be
used, HP steel (for offensive and STAB purposes) or
Ancient power (for a chance to boost all stats, but
its low PP may be its let down).

EV Corner:

Max out the EVs in HP and Speed for Mawile with any remaining in Defense

Strategy Against Mawile

Mawile is quite an underestimated Pokémon. Although it
lacks in Speed, HP and Specials, it has decent Attack
and Defence, both of which can be improved with Sword
Dance and Iron Defence (and on the odd occasion,
Ancient Power).
- Since most Mawiles will have Taunt Hazing away any
stat boosts it makes may not be as easy as it seems.
Personally, I'd suggest sending out a Pokémon with a
Fire Attack immediately, forcing a switch or forcing
them to see their Mawile lose all its stats.
- Earthquakes (and STAB fighting attacks) are also
viable options if Mawile hasn't used Iron Defence,
however you should put less reliance on them being
fully effective since Mawile has decent defence and
may take a couple of hits.
- Taunt could quite easily mess with Passing Mawile as
well, since that would disable all of Mawile's main
moves for a couple of turns and allow it to be pounded
by your offence.
- Magnet Pull is okay (as far as I know it doesn't
block Baton Pass though), and even Fire Punching
Nosepass has a chance at Knocking Out Mawile in a
couple of hits (though that's just an example of how
low Mawile's Special Defence is, Nosepass would most
likely get owned by HP Steel), however Mawile can just
Baton Pass out of the situation so make sure you get
the job done quickly, all that Magnet pull does is
make sure that if it's slower it can't just switch out
manually.

Contest Moveset

A good Contest Moveset for Mawile would have to be this for the Cool Contest best with Lonely, Adament, Naughty or Brave Nature:

Attacks:

Sunny Day
Flamethrower
Fire Blast
Hyper Beam

Items Attached:

Red Scarf

Strategy Using Mawile

If you do the attacks in this following order you should have very few problems; 1st - Sunny day, 2nd - Flamethrower, 3rd - Sunny Day, 4th - Fire blast, 5th - Hyperbeam